Chair construction



1958 J. F. MELBOURNE ET AL 2,865,498

CHAIR CONSTRUCTION Filed Dec. 51, 1957 INVENTORS JOSEPH F- MELBOURNE LOUIS SKATOFF &

Ml HAEL ALFE D FIG. 2 BY flgmu ATTORN EY 2,866,498 Patented Dec. 30,1958

CHAIR CONSTRUCTION Joseph F. Melbourne, St. Louis, and Louis Skatoff and Michael Alt'end, University City, Mo.

Application December 31, 1957, Serial No. 706,418

3 Claims. (Cl. 155-193) resisted at the attachmentof such seat backs to chair seat structures. Further purposes are: to use laminated wood structure in combination with steel back posts in such manner as facilitates'assembly, and yet to effect an elastic distribution of the bending loads applied to the back. of the chair.

These and other objects, which will be apparent from the specification, are achieved in the structure hereinafter described and illustrated in the drawings, in which:

Figure 1 is a perspective view showing the general organization of a chair seat and back structure embodying the present construction.

Figure 2 is a sectional view taken along line 22 of Figure 1, showing the structure with a swivel-pedestal attached.

Figure 3 is a free-body diagram showing the U-shaped laminated board member of Figures 1 and 2 under a simple system of loads, the dashed line indicating deflection of its upper margin.

The chair seat structure shown in Figures 1 and 2 includes a U-shaped laminated board generally designated 11, preferably formed of vertically-extending, bent plies of wood securely glued together, which serves as the principal seat frame member. The thickness of the laminated board 11 is substantially less than its height, as shown. Its ends 12 are positioned to extend forward; it has straight side portions 13 and a curved back portion 14.

Extending across between the ends 12 of the U-shaped laminated board 11, and secured thereto by corner glue blocks 15, is a straight front board 16 which serves as the front member of the seat structure. Its height is the same as that of the U-shaped laminated board 11; together they form the frame which extends around the entire seat structure. Affixed to its aft side by nails, screws or other joining means and securely glued thereto, is a straight horizontal front support bar 17; similarly secured to and fitting within the curve of the back portion 14 is a curved aft support bar 18. Fore-and-aft stretcher beams 19 are located beneath and bear against the under sides of the support bars 17, 18. These stretcher beams 19 are located one to the left and one to the right of a central fore-and-aft plane of symmetry, and extend between and join the front board 16 to the back portion 14, preferably at their base portions and in any event well below their mid-heights.

Substantially the entire space inside the U-shaped laminated board 11 and front board 16, and above the stretcher beams 19, is open and thus available for filling by the use of conventional upholstery materials if desired. We prefer," however, to utilize the strength of the U-shaped board 11 and front board 16 to attach to the upper edge thereof relatively flat undulating springs 20 with nailed end clips 21. The springs 20 may be tied with fabric to said upper edge as by the fabric ties 22, and be resiliently supported between themselves by helical coils 23, all above the top surface of the chair structure.

Beneath the stretcher beams 19 may be mounted chair support structure such as the central pedestal structure shown in Figure 2 and consisting of an upper swivel plate 24, a lower swivel plate 25 and outWard-and-downward extending legs 26.

Upper and lower plate nuts 27, 28 respectively, driven into pairs of aligned bores above and below the mid-. height of the back portion 14 at each side of the plane of symmetry, are utilized to secure substantially horizontal bolts 29 inside the chair seat structure, where they penetrate through upper and lower bores 30, 31 through the lower portions of left and right back posts 32, inwardly adjacent the curved back portion 14 of the laminated board 11. The back posts 32 may be sturdy tubular steel, bent slightly backward at bends 33 near their midheight, and having in the portion above the bends 33 upper and lower fore-and-aft bores 34, 35 respectively. While the bores 30, 31, 34 and 35 in the metal posts 32' are referred to as extending fore-and-aft, their actual di rection will conform and be perpendicular to the curva-' ture of the wooden members which they secure.

Above their bends 33, theback posts 32 are accommodated between a pair of curved plywood plates, the forward seat-back plate 36 and the aft seat-back plate, 37, spaced from each other by side filler blocks 38 and atop central filler block 39. Bolts 40 through the forward seat-back plate extend through the upper and lower foreand-aft bores 34, 35 in the back posts 32,. and onto them are tightened nuts 41 accessible through fairly large cleared holes 42 in the aft seat-back plate 37.

When a person sitting 'in a chair tilts it backward, he may exert a large force downward and aft against the seat back. The downward component may be resisted by the upward reaction on the rear legs of the chair. Bending loads are induced at the juncture of the seat structure with the back structure; in case of the present structure, in the metal posts below the bend 33 and throughout the attachment of the lower post portions to the U-shaped laminated board 11. These bending loads exert stresses extending to points in the structure where other forces counteract them and establish a condition of static equilibrium.

In the sketch, Figure 3, a free-body diagram of the external forces affecting the U-shaped laminated board, the vertical arrows at the curved back portion 14 of the laminated board indicate the excess of upward forces, applied by the rear ends of the stretcher beams 19, over the downward forces which may be transmitted through the back posts 32. The curved arrows represent the bending moment from the back posts, applied to the back portion 14 to twist it as if in torsion. Such bending moment may be reacted by a downward force exerted by the front board, as represented by the downward-pointing arrows at the front ends 12 of the side portions 13. The reactions from the pedestal are transmitted through the stretcher beams 19; they also serve to prevent the lower end of the back portion 14 from twisting inward, and exerting an aft force on the lower portion thereof. The reaction of this force is shown by the forward arrows at the front ends 12, which reaction is imparted through the front board 16.

When bending forces which impose such twisting moments are resisted elastically in the U-shaped laminated board by deflection, the upper margin of the board 11 is drawn somewhat outward at the back portion 14 and somewhat inward along the sides 13, as shown somewhat exaggerated in Figure 3. Below its mid-height, however, it is stabilized by the aft reaction of the stretcher beam 19.

A degree of elasticity is thus provided, sufiicient to minimize breakage under sudden applications of load. The very simple attachment of the lower portions of the back posts 32 distributes the bending load into the U- shaped laminated board 11, whose strength and resiliency are thus availedof to. resist the bending loads applied to the chair back.

Modifications will occur to those familiar with the problems of chair construction; hence this invention is not to be construed narrowly, but fully coextensive with the claims.

We claim:

1. Chair construction comprising a seat portion including a U-shaped seat frame member forming the sides and back of the seat portion and having forwardly-presented ends, a seat front member joining the said ends of said seat frame member throughout their entire depth, seat support structure including a support beam having a front end joined to the seat front member and a rear end joned to part of the. back of the. seat frame member below its mid-height, further comprising a back post having a lower end portion joined to the inner side of the back portion of the seat frame member,.said back post having an upper end portion, and seat back structure secured thereto, whereby forces applied to the seat back to impose bending loads on the back post are elastically resisted by deflecting the U-shaped seat frame member.

2. In chair construction, a seat portion including a seat frame having a front, sides and back, each being higher vertically than its thickness and together providing a continuous upper edge, spring elements secured to said upper edge and extending thereacross, a support beam joining the front of the seat frame to the rear thereof at a level below its mid-height, and a pair of back posts having lower end portions secured to and against the inner side of the back portion of the seat frame and having securement means joining it thereto both above and below its mid-height, said back posts having upper end portions, and seat-back structure secured thereto, whereby forces applied to the seat back tend to bend the portion of the seat frame above its mid-height elastically out of alignment.

3. In chair construction, a front board extending from one side of the chair to the other whereby to establish the front of seat structure therefor, a U-shaped laminated board joining and extending from one end of the front board aft and thence around and thence forward to the other end of the front board, whereby to establish side portions and a back portion of the seat structure, said front, side and back portions having upper edges at the same level, a stretcher beam joined to and extending from the front board, aft to and connecting with the back portion of the U-shaped laminated board, together with metal back posts having lower ends forwardly adjacent the back portion of the U-shaped laminated board, and having connections thereto positioned sidewards of the stretcher beam, said metal posts having upper ends, and a seat back supported thereby, whereby forces applied to the seat back to impose bending moments on the back posts are resiliently resisted at their connection to the back portion of the U-shaped laminated board by deflection thereof.

References Cited in the filc of this patent UNITED STATES PATENTS 170,554 Hale Nov. 30, 1875 1,007,006 Ordway Oct. 24, 1911 1,780,570 Stephens Nov. 4, 1930 2,146,136 Foote Feb. 7, 1939 FOREIGN PATENTS 74,292 Austria Apr. 10, 1918 469,396 Great Britain July 26, 1937 

